1. Field of the Invention
The present specification relates to a reactor in which a reactor body is fixed to a heat sink through a heat transfer sheet.
2. Description of Related Art
Japanese Patent Application Publication No. 2013-118208 (JP 2013-118208 A) discloses a technology for structuring a reactor body by covering a core with a bobbin and winding a coil around the bobbin. When the reactor body operates, heat is generated. In JP 2013-118208 A, a device is disclosed, in which the reactor body is fixed to a heat sink. In JP 2013-118208 A, in order to reduce heat resistance from the reactor body to the heat sink, a heat transfer sheet is interposed between the reactor body and the heat sink. In this specification, a device in which a reactor body is fixed to a heat sink through a heat transfer sheet is referred to as a reactor.
The heat transfer sheet needs to closely adhere to both the reactor body and the heat sink, and also needs to be flexible. Because a phenomenon of generating heat during an operation and cooling down when the operation ends is repeated in the reactor body, the heat transfer sheet is also exposed to a heating and cooling cycle. Since the heat transfer sheet is flexible, its thermal expansion coefficient is large. Because the heat transfer sheet having a large thermal expansion coefficient is exposed to a heat cycle, the heat transfer sheet repeats an expansion and contraction cycle. With the heat cycle, the reactor body and the heat sink that sandwich the heat transfer sheet also repeat an expansion and contraction cycle. Therefore, a range of expansion and contraction of the heat transfer sheet is increased. It is necessary to keep heat transfer sheet closely adhering to both the reactor body and the heat sink against the expansion and contraction cycle.
In JP 2013-118208 A, an expansion of the heat transfer sheet is prevented by allowing an end edge of the heat transfer sheet to abut on a side surface of a recess provided in the heat sink. The side surface is referred to as an expansion restricting wall. In JP 2013-118208 A, a structure is employed in which the rectangular heat transfer sheet is housed in a rectangular recess, and the entire length of an end edge of the heat transfer sheet in four peripheral sides abuts on the expansion restricting wall.